Non-Targeted Tandem Mass Spectrometry Analysis Reveals Diversity and Variability in Aerosol Functional Groups Across Multiple Sites, Seasons, and Times of Day

Organic aerosol (OA) is a complex mixture of compounds with diverse elemental and structural features, whose composition affects its health and environmental impacts. A detailed speciation of the functional group distribution in OA is important for constraining atmospheric reaction pathways and products, evaluating chemical mechanisms and models, and understanding OA impacts. We used high-resolution tandem mass spectrometry to perform a non-targeted analysis of OA functional groups from three diverse ambient sites across time of day and season. We observed a range of oxygen-, nitrogen- and/or sulfur-containing functional groups, including oxygenates such as hydroxyls (29-69%) and carboxylic acids (19-59%) that dominated the functional group distribution and that may participate in hydrogen bonding and thus impact OA chemical/physical properties (percentages indicate average ion abundance contributions across campaigns). We also observed esters (7-39%) and ethers (13-42%) that suggest the importance of oli...